SENSITIVE LIQUID-CHROMATOGRAPHIC DETERMINATION OF ALKYL-PHENOLS, NITRO-PHENOLS AND CHLOROPHENOLS BY PRECOLUMN DERIVATIZATION WITH DANSYL CHLORIDE, POSTCOLUMN PHOTOLYSIS AND PEROXYOXALATE CHEMILUMINESCENCE DETECTION

A liquid chromatographic method is described for the determination of alkyl-, nitro- and chlorophenols at sub-ppb levels using a very sensitive and selective detection system. The phenols are labelled by two an organic phase in which dansyl chloride is dissolved. After derivatization, the excess of reagent is removed on an amino-bonded column; dansyl chloride reacts with the amino groups whereas the phenol derivatives are not retained. Chromatography is carried out with a methanol-water gradient followed by photolysis of the derivatives. The strongly quenching electronegative nitro- and chlorophenol groups are photochemically removed from the derivative and the products, dansyl hydroxide and dansyl methoxide, are sensitively detected by peroxyoxalate chemiluminescence. Chemical excitation is carried out by adding 2-nitrophenyl oxalate and hydrogen peroxide dissolved in acetonitrile to the column eluate. Detection limits of about 0.01-0.1 ng/ml have been achieved and the method has been applied to the determination of several phenolic compounds in surface water.